Detecting the electrical circuit that corresponds to an electrical outlet is a critical safety practice required for doing any major electrical work. Older houses and businesses have typically undergone numerous changes to their electrical systems over time, and the changes in some instances may be poorly or inaccurately documented. Also, circuit marking may become illegible on the circuit boxes. Moreover, especially in older buildings, the outlets in a single room may not all be on the same circuit, since electricians or other workers adding additional service may just tap into the nearest wire rather than trying to tap into the circuit that corresponds to other outlets in the room. As a result, detecting and mapping circuit breakers to outlets can be long and tedious process.
One method for mapping circuit breakers to outlets consists of flipping switches and yelling. In this scenario, one person flips all of the switches on the circuit-breaker box. Another person waits in another room and yells when the lights or other devices go off (i.e., lose power). They then double-check the circuits. This approach requires no technology, but it is time consuming. In addition to being time consuming, this approach requires two people for it to be practical.
Another approach is to use a commercially available device that connects to an outlet and sends a signal over the electrical line from the outlet to the circuit breaker. The electrician then moves a detector over the circuit breakers. The detector picks up the signal when it passes over the circuit for the outlet with the signaling device attached and typically lights up or emits a tone. While this approach can be carried out by one person and is less time consuming than the previous method for a single outlet, it is not efficient for mapping a larger number of outlets. This is because the detectors can not differentiate between signals sent from different modules, so multiple signal-sending modules cannot be detected in parallel. That is, if an electrician were to plug modules into multiple outlets that were not all on the same circuit, there would be no way to tell which outlets were on which circuit.
A method for collecting information about different outlets and consolidating the information into a hand-held computer is described in U.S. Pat. No. 7,057,401. This approach allows a technician to collect signals from multiple modules in parallel, but this approach is cumbersome, requiring that the outlets and circuit box be connected by an additional wire (“umbilical cord”) that needs to be carried around the worksite. Moreover, this approach is expensive, due to the computer and the umbilical cord.
U.S. Pat. No. 6,466,029 provides a method for detecting the correct circuit interrupt device for a particular circuit by applying a signal generator at an outlet and sweeping a signal detector over circuit interrupt devices. This method only allows for one to one correlation of an outlet and a fuse or circuit breaker. Similarly, U.S. Pat. No. 5,493,206 provides a method and apparatus for determining a group to which a connection point forming part of an electrical installation belongs by installing a detector in place of a fuse and generating a signal at a connection point. This method only allows for one to one correlation of an outlet and a fuse or circuit breaker. This method is limited by the scalability of the number of connections that can be made simultaneously to the fuse box.
A method for determining which outlet is closer to a circuit breaker is described in U.S. Pat. No. 5,352,985. In this method a device measures a voltage drop over a wiring loop between neutral and earth contact terminals. This approach, however, only tells the electrician about the relative proximity to the circuit breaker after he knows that they are on the same circuit.
Each of the foregoing approaches requires setup time and an assortment of equipment. Moreover, in the foregoing approaches a circuit interrupt device is detected for a single outlet or connection point at a time. In some cases an electrician may wish to know which outlets are on the same circuit without an elaborate setup process. For example, he might want to determine if a device that should not be turned off (such as a refrigerator or a clock that is going to have to be reset) is going to be affected by turning off a circuit. He also might already know which circuit one outlet is on and want to quickly determine whether other outlets are on the same circuit.